Create the project
Open Worldkiln. Create a project from Home and open its World.
Build the floor
Choose Block placement and make a small floor. Put a SpawnPoint above it. Leave space for the Player to move.
Test
Start Play. The Player should appear above the floor and land on it. Walk around, then stop Play. If the Player falls, check the floor's solid setting and the SpawnPoint position. Save the World after making authored changes.
Next
Follow Your first script. For tool details, see Building.